PERC-UPC - Power Electronics Research Centre
Total activity: 3729
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PERC
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ETSEIB. Edifici H. Despatx 9-24. Av. Diagonal, 647 Open in new window
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Barcelona
URL
http://held.perc.upc.edu/?set_language=es Open in new window
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PERC-UPC - Centre de Recerca d'Electrònica de Potència UPC

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1 to 50 of 3729 results
  • Development and testing of a bidirectional distribution electronic power transformer model

     Alepuz Menendez, Salvador; González, Francisco; Martín-Arnedo, Jacinto; Martinez Velasco, Juan Antonio
    Electric power systems research
    Date of publication: 2014-02
    Journal article

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    Transformer size can be significantly reduced by increasing the operating frequency, which may be achieved by means of power electronics converters installed as interfaces to the power frequency systems at both transformer sides. In this work, a model for a bidirectional high-frequency power electronic transformer is presented. Several case studies have been carried out in order to evaluate the behavior of the transformer under different operating conditions and test the impact on the power quality. The results show that the electronic power transformer, also known as solid-state transformer, not only matches the functions of a conventional power transformer, but also provides additional capabilities to mitigate dynamic power quality problems.

  • Redesign process of a 765 kV AC substation connector by means of 3D-FEM simulations

     Hernandez Guiteras, Joan; Riba Ruiz, Jordi Roger; Romeral Martinez, Jose Luis
    Simulation modelling practice and theory
    Date of publication: 2014-03-03
    Journal article

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    This paper shows the capabilities of applying the three-dimensional finite element method (3D-FEM) for designing complex-shaped substation connectors to operate at 765 kVRMS AC. To check this methodology, it was analyzed the feasibility of upgrading a 400 kVRMS substation connector to operate at 765 kVRMS. However, both experimental and simulation results conducted according to the ANSI/NEMA CC 1-2009 standard concluded that although it passed the visual corona test, to ensure a wide safety margin it was desirable an improvement of the electrical behavior of such connector. It was shown that FEM results allowed detecting the peak stress points of the connector regarding the electrical stress thus allowing applying a corrective action. Then, two possible solutions were analyzed, i.e. the use of corona shields and the redesign of the connector assisted by 3D-FEM simulations. Results presented in this work show that both approaches have an excellent behavior in reducing the electric field strength on the connector surface. However, to make the final decision, the production cost of both alternatives was analyzed, thus favoring the redesign option. Next, the redesigned version of the substation connector was manufactured and tested. Experimental results conducted in a high voltage laboratory verified the effectiveness of the methodology and the potential of the proposed system to act as an advanced design tool for optimizing the behavior of complex-shaped substation connectors. Thus, this system allows assisting efficiently the design process while permitting constraining the economic costs

  • Reduction of Output Common Mode Voltage Using a Novel SVM Implementation in Matrix Converters for Improved Motor Lifetime

     Espina, Jordi; Ortega, Carlos; De Lilo, Liliana; Empringham, Lee; Balcells Sendra, Josep; Arias Pujol, Antoni
    IEEE transactions on industrial electronics
    Date of publication: 2014-11-01
    Journal article

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    This paper presents the study of an alternative space vector modulation (SVM) implementation for matrix converters (MCs), which reduces the output common mode (CM) voltage. The strategy is based on replacing the MC zero vectors with rotating ones. In doing this, the CM voltage (CMV) can be reduced, which, in turn, reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the induction motor (IM) deterioration can be slowed down. This paper describes the SVM pattern and analyzes the CMV and the leakage current paths. Simulation and experimental results based on an MC-IM drive are provided to corroborate the presented approach.

    This paper presents the study of an alternative Space Vector Modulation (SVM) implementation for Matrix Converters (MC) which reduces the output Common Mode (CM) voltage. The strategy is based on replacing the MC zero vectors by the rotating ones. In doing this, the CM voltage can be reduced which in-turn reduces the CM leakage current. By reducing the CM current, which flows inside the motor through the bearings and windings, the Induction Motor (IM) deterioration can be slowed down. The paper describes the SVM pattern and analyses the CM voltage and the leakage current paths. Simulation and experimental results based on a MC-IM drive are provided to corroborate the presented approach.

  • Minimum signal modulation scheme based on a single carrier for interleaved operation of parallel phase legs in voltage source converters

     Capella Frau, Gabriel Jose; Gabiola Antxustegi, Igor; Pou Felix, Josep; Zaragoza Bertomeu, Jordi; Ceballos Recio, Salvador; Agelidis, Vassilios
    IET power electronics
    Date of publication: 2014-05-01
    Journal article

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    Connecting legs in parallel is a common way to increase the output current of a power converter. Interleaving the carriers used to modulate the reference signals for each leg leads to a reduction in the output current ripple without resorting to increasing the switching frequency. A whole set of shifted carriers is required if interleaved pulse-width modulators (PWMs) are used. Implementing this by means of a digital signal processor (DSP) means that the higher the number of carriers, the higher the number of DSP timing resources required. Provided that the latter are usually limited, this could be a drawback when increasing the number of interleaved carriers. This study presents the implementation of a PWM scheme where all modulators use the same carrier offering the same results as if a set of n interleaved carriers were used. Since the proposed algorithm takes maximum benefit from the PWM units available in a DSP, a higher number of legs connected in parallel can be controlled without adding any external processing hardware. A MATLAB/Simulink model has been set up for simulation purposes. Selected experimental results obtained from a three-leg single-phase inverter are reported, confirming the effectiveness of the proposed implementation. © The Institution of Engineering and Technology 2014.

  • Environmental assessment of small-scale production of wood chips as a fuel for residential heating boilers

     Esteban Dalmau, Bernat; Riba Ruiz, Jordi Roger; Baquero Armans, Grau; Puig Vidal, Rita; Rius Carrasco, Antoni
    Renewable energy
    Date of publication: 2014-02
    Journal article

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    This work performs a comparative life cycle assessment (LCA) of two fuels for heating boilers, namely wood chips and oil. The LCA methodology allows comparing the environmental impacts of the two analyzed fuels, thus assessing which is environmentally more advantageous. The study is focused on Mediterranean forests located in the Argençola region (Catalonia, northeastern Spain) by applying forest management practices focused to ensure a sustainable exploitation. The direct use of wood chips as a fuel for boilers simplifies notably the number of processes involved in producing such a fuel. The results presented clearly show the environmental benefits of using small-scale produced wood chips instead of fossil oil by analyzing representative impact categories defined by the CML and EDIP methods, even when considering the changes in the carbon stock in the forests under analysis due to the management approach adopted. A sensitivity analysis has also been conducted to assess the impact of the data with higher uncertainty on the final LCA results.

  • Voltage support control strategies for static synchronous compensators under unbalanced voltage sags

     Castilla Fernandez, Miguel; Miret Tomas, Jaume; Camacho Santiago, Antonio; Matas Alcala, Jose; Garcia de Vicuña Muñoz de la Nava, Jose Luis
    IEEE transactions on industrial electronics
    Date of publication: 2014
    Journal article

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    Static synchronous compensators have been broadly employed for the provision of electrical ac network services, which include voltage regulation, network balance, and stability improvement. Several studies of such compensators have also been conducted to improve the ac network operation during unbalanced voltage sags. This paper presents a complete control scheme intended for synchronous compensators operating under these abnormal network conditions. In particular, this control scheme introduces two contributions: a novel reactive current reference generator and a new voltage support control loop. The current reference generator has as a main feature the capacity to supply the required reactive current even when the voltage drops in amplitude during the voltage sag. Thus, a safe system operation is easily guaranteed by fixing the limit required current to the maximum rated current. The voltage control loop is able to implement several control strategies by setting two voltage set points. In this paper, three voltage support control strategies are proposed, and their advantages and limitations are discussed in detail. The two theoretical contributions of this paper have been validated by experimental results. Certainly, the topic of voltage support is open for further research, and the control scheme proposed in this paper can be viewed as an interesting configuration to devise other control strategies in future works.

    Static synchronous compensators have been broadly employed for the provision of electrical ac network services, which include voltage regulation, network balance, and stability improvement. Several studies of such compensators have also been conducted to improve the ac network operation during unbal- anced voltage sags. This paper presents a complete control scheme intended for synchronous compensators operating under these abnormal network conditions. In particular, this control scheme introduces two contributions: a novel reactive current reference generator and a new voltage support control loop. The current reference generator has as a main feature the capacity to supply the required reactive current even when the voltage drops in amplitude during the voltage sag. Thus, a safe system operation is easily guaranteed by fixing the limit required current to the maximum rated current. The voltage control loop is able to imple- ment several control strategies by setting two voltage set points. In this paper, three voltage support control strategies are proposed, and their advantages and limitations are discussed in detail. The two theoretical contributions of this paper have been validated by experimental results. Certainly, the topic of voltage support is open for further research, and the control scheme proposed in this paper can be viewed as an interesting configuration to devise other control strategies in future works.

  • Experimental Investigations into the Effects of Electrical Stress on Electromagnetic Emission from Integrated Circuits

     Boyer, Alexandre; Dhia, Sonia Ben; Li, Binhong; Berbel Artal, Nestor; Fernández García, Raúl
    IEEE transactions on electromagnetic compatibility
    Date of publication: 2014-02-01
    Journal article

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    Recent studies have shown that the aging of integrated circuits may modify electromagnetic emission significantly. This paper reports on an experiment to elucidate the origins of emission level changes in a test chip using 90-nm CMOS technology. Circuit analysis, combined with electromagnetic emission and on-chip power supply voltage bounce measurements made during the application of electric stress, have identified the role of intrinsic wear-out mechanisms, which contribute to a progressive change in the transient current produced by the circuit.

    Recent studies have shown that the aging of integrated circuits may modify electromagnetic emission significantly. This paper reports on an experiment to elucidate the origins of emis- sion level changes in a test chip using 90-nm CMOS technology. Circuit analysis, combined with electromagnetic emission and on- chip power supply voltage bounce measurements made during the application of electric stress, have identified the role of intrinsic wear-out mechanisms, which contribute to a progressive change in the transient current produced by the circuit.

  • Detection of interturn faults in PMSMs with different winding configuration

     Saavedra Ordoñez, Harold; Urresty Betancourt, Julio; Riba Ruiz, Jordi Roger; Romeral Martinez, Jose Luis
    Energy conversion and management
    Date of publication: 2014-03-03
    Journal article

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    Interturn faults in permanent magnet synchronous motors (PMSMs) may develop fast into more severe faults such as coil-to-coil, phase-to-phase and phase-to-ground short circuits. These faults are very destructive and may irreversibly damage the PMSM. Therefore, it is highly desirable to develop suitable methods for the early detection of such faults. The effects of interturn faults are visible in both the stator currents and the zero-sequence voltage component (ZSVC) spectra. By designing appropriate fault diagnosis schemes based on the analysis of the harmonic content of such electric variables it is possible to detect short circuit faults in its early stage. However, the stator winding configuration of the PMSM deeply impacts the harmonic content of both spectra. This paper studies the effects of different stator winding configurations in both the stator currents and the ZSVC spectra of healthy and faulty machines. Results presented may help to develop fault diagnosis schemes based on the acquisition and further analysis of the stator currents and/or the ZSVC harmonic components.

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    Reactive Power Control for Distributed Generation Power Plants to Comply With Voltage Limits During Grid Faults  Open access

     Camacho Santiago, Antonio; Castilla Fernandez, Miguel; Miret Tomas, Jaume; Guzman Sola, Ramon; Borrell Sanz, Angel
    IEEE transactions on power electronics
    Date of publication: 2014-11-01
    Journal article

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    Grid faults are one of the most severe problems for network operation. Distributed generation power plants can help to mitigate the adverse effects of these perturbations by injecting the reactive power during the sag and the postfault operation. Thus, the risk of cascade disconnection and voltage collapse can be reduced. The proposed reactive power control is intended to regulate the maximum and minimum phase voltages at the point of common coupling within the limits established in grid codes for continuous operation. In balanced three-phase voltage sags, the control increases the voltage in each phase above the lower regulated limit by injecting the positive sequence reactive power. In unbalanced voltage sags, positive and negative sequence reactive powers are combined to flexibly raise and equalize the phase voltages; the maximum phase voltage is regulated below the upper limit and the minimum phase voltage just above the lower limit. The proposed control strategy is tested by considering a distant grid fault and a large grid impedance. Selected experimental results are reported in order to validate the behavior of the control scheme.

    Grid faults are one of the most severe problems for network operation. Distributed generation power plants can help to mitigate the adverse effects of these perturbations by injecting reactive power during the sag and the post-fault operation. Thus, the risk of cascade disconnection and voltage collapse can be reduced. The proposed reactive power control is intended to regulate the maximum and minimum phase voltages at the point of common coupling within the limits established in grid codes for continuous operation. In balanced three-phase voltage sags, the control increases the voltage in each phase above the lower regulated limit by injecting positive sequence reactive power. In unbalanced voltage sags, positive and negative sequence reactive powers are combined to flexibly raise and equalize the phase voltages; maximum phase voltage is regulated below the upper limit and the minimum phase voltage just above the lower limit. The proposed control strategy is tested by considering a distant grid fault and a large grid impedance. Selected experimental results are reported in order to validate the behavior of the control scheme.

  • Runout tracking in electric motors using self-mixing interferometry

     Atashkhooei, Reza; Urresty Betancourt, Julio; Royo Royo, Santiago; Riba Ruiz, Jordi Roger; Romeral Martinez, Jose Luis
    IEEE-ASME transactions on mechatronics
    Date of publication: 2014-01-17
    Journal article

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  • Fixed frequency sliding mode-based robust inversion with a full-bridge current DC-link buck-boost

     Olm Miras, Josep Maria; Biel Sole, Domingo; Fossas Colet, Enric; Cardoner Parpal, Rafael
    Journal of the Franklin Institute
    Date of publication: 2014-01
    Journal article

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    The substitution of the original switches by a full bridge in a Non-Inverting Buck-Boost converter results in an inverter capable of carrying out step-down and step-up tasks as well under sliding mode control. The control law is implemented by means of the Zero Average Dynamics algorithm, which provides a fixed frequency operation and guarantees null error in each switching period, thus achieving a highly accurate tracking of periodic reference profiles. Furthermore, semi-infinite programming techniques are used to reduce power losses and, at the same time, prevent undesirable effects of control action saturation. The performance of the inverter is ensured to be robust in the face of bounded nonlinear and resistive loads. Realistic simulation results obtained with PSIMR software validate the proposed schemes.

    The substitution of the original switches by a full bridge in a Non-Inverting Buck-Boost converter results in an inverter capable of carrying out step-down and step-up tasks as well under sliding mode control. The control law is implemented by means of the Zero Average Dynamics algorithm, which provides a fixed frequency operation and guarantees null error in each switching period, thus achieving a highly accurate tracking of periodic reference profiles. Furthermore, semi-infinite programming techniques are used to reduce power losses and, at the same time, prevent undesirable effects of control action saturation. The performance of the inverter is ensured to be robust in the face of bounded nonlinear and resistive loads. Realistic simulation results obtained with PSIMR software validate the proposed schemes.

  • Design-oriented analysis of quantization-induced limit cycles in a multiple-sampled digitally controlled buck converter

     Bradley, Mark; Alarcon Cot, Eduardo Jose; Feely, Orla
    IEEE transactions on circuits and systems I: regular papers
    Date of publication: 2014-04-01
    Journal article

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    Digital control of switching power converters is an area which has seen increased attention in recent years. However, quantization in the feedback loop from the analog-to-digital (A/D) converter and the digital pulse width modulator (DPWM) may cause limit cycle oscillations to manifest, which are generally seen as being undesirable. This paper presents an analysis of the limit cycle behavior found in a multiple-sampled digitally controlled buck converter. The limit cycles which may arise in the system are characterized and conditions to prevent these oscillations from occurring are presented. © 2004-2012 IEEE.

    Digital control of switching power converters is an area which has seen increased attention in recent years. However, quantization in the feedback loop from the analog-to-digital (A/D) converter and the digital pulse width modulator (DPWM) may cause limit cycle oscillations to manifest, which are generally seen as being undesirable. This paper presents an analysis of the limit cycle behavior found in a multiple-sampled digitally controlled buck converter. The limit cycles which may arise in the system are characterized and conditions to prevent these oscillations from occurring are presented. © 2004-2012 IEEE.

  • Experimentally compared fuel consumption modelling of refuse collecting vehicles for energy optimization purposes

     Soriano, Franciso; Alvarez Florez, Jesus Andres; Moreno Eguilaz, Juan Manuel
    SAE international journal of commercial vehicles
    Date of publication: 2014-05
    Journal article

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    This paper presents a novel methodology to develop and validate fuel consumption models of Refuse Collecting Vehicles (RCVs). The model development is based on the improvement of the classic approach. The validation methodology is based on recording vehicle drive cycles by the use of a low cost data acquisition system and post processing them by the use of GPS and map data. The corrected data are used to feed the mathematical energy models and the fuel consumption is estimated. In order to validate the proposed system, the fuel consumption estimated from these models is compared with real filling station refueling records. This comparison shows that these models are accurate to within 5%.

    This paper presents a novel methodology to develop and validate fuel consumption models of Refuse Collecting Vehicles (RCVs). The model development is based on the improvement of the classic approach. The validation methodology is based on recording vehicle drive cycles by the use of a low cost data acquisition system and post processing them by the use of GPS and map data. The corrected data are used to feed the mathematical energy models and the fuel consumption is estimated. In order to validate the proposed system, the fuel consumption estimated from these models is compared with real filling station refueling records. This comparison shows that these models are accurate to within 5%.

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    A Combined Methodology of Adaptive Neuro-Fuzzy Inference System and Genetic Algorithm for Short-term Energy Forecasting  Open access

     Kampouropoulos, Konstantinos; Andrade Rengifo, Fabio; Garcia Espinosa, Antonio; Romeral Martinez, Jose Luis
    Advances in Electrical and Computer Engineering
    Date of publication: 2014-02-01
    Journal article

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    This document presents an energy forecast methodology using Adaptive Neuro-Fuzzy Inference System (ANFIS) and Genetic Algorithms (GA). The GA has been used for the selection of the training inputs of the ANFIS in order to minimize the training result error. The presented algorithm has been installed and it is being operating in an automotive manufacturing plant. It periodically communicates with the plant to obtain new information and update the database in order to improve its training results. Finally the obtained results of the algorithm are used in order to provide a short-term load forecasting for the different modeled consumption processes.

    This document presents an energy forecast methodology using Adaptive Neuro-Fuzzy Inference System (ANFIS) and Genetic Algorithms (GA). The GA has been used for the selection of the training inputs of the ANFIS in order to minimize the training result error. The presented algorithm has been installed and it is being operating in an automotive manufacturing plant. It periodically communicates with the plant to obtain new information and update the database in order to improve its training results. Finally the obtained results of the algorithm are used in order to provide a shortterm load forecasting for the different modeled consumption processes.

  • Performance improvement of a prefiltered synchronous-reference-frame PLL by using a PID-type loop filter

     Golestan, Saeed; Monfared, Mohammad; Freijedo Fernández, Francisco Daniel; Guerrero Zapata, Josep Maria
    IEEE transactions on industrial electronics
    Date of publication: 2014-07-01
    Journal article

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    Control Parameters design of a three-phase synchronous reference frame phase locked loop (SRF-PLL) with a prefiltering stage (acting as the sequence separator) is not a trivial task. The conventional way to deal with this problem is to neglect the interaction between the SRF-PLL and prefiltering stage, and treat them as two separate systems. This approach, although very simple, is not optimum as the prefiltering stage and the SRF-PLL may have comparable dynamics. The aim of this paper is to develop a systematic and efficient approach to design the control parameters of the SRF-PLL with prefiltering stage. To this end, the paper first optimizes the performance of the prefiltering stage in detection of the sequence components. The paper then proceeds to reduce the interaction between the prefiltering stage and SRF-PLL, which is achieved by employing a derivative-filtered proportional-integral-derivative controller as the loop filter (instead of the commonly adopted proportional-integral controller) and arranging a pole-zero cancellation. The suggested method is simple and efficient, and is applicable to the joint operation of different sequence separation techniques and the SRF-PLL. The effectiveness of the suggested design approach is confirmed through extensive experimental results.

  • Modeling and design of voltage support control schemes for three-phase inverters operating under unbalanced grid conditions

     Castilla Fernandez, Miguel; Miret Tomas, Jaume; Camacho Santiago, Antonio; Garcia de Vicuña Muñoz de la Nava, Jose Luis; Matas Alcala, Jose
    IEEE transactions on power electronics
    Date of publication: 2014-11-01
    Journal article

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    Three-phase inverters equipped with voltage support control schemes have been successfully used to alleviate the negative impact of voltage imbalance on electric power systems. With these schemes, dc-link voltage ripple and current harmonics are significantly reduced by processing the positive and negative sequence components separately. However, the design methods for tuning the parameters of these control schemes have one or more of the following limitations: 1) the design is a very time-consuming task, 2) it is conservative, 3) it does not guarantee the specifications for all the considered situations, and 4) the system can be unstable in some abnormal conditions. As an alternative, this paper presents a design method based on the analysis of oscillations in nonlinear systems. The method proceeds by first developing simple and accurate models of the power system, second it reveals the system features through an in deep analysis of the derived models, and third it introduces a systematic design procedure for tuning the parameters of the control schemes. As an example, a voltage support control scheme for a three-phase inverter operating under an unbalanced voltage sag is designed and validated experimentally.

  • Maximum power point tracking based on slidingmode control for output-series connected converters in photovoltaic systems

     Cabal, Cédric; Martínez Salamero, Luis; Séguier, Lionel; Alonso, Corinne; Guinjoan Gispert, Francisco
    IET power electronics
    Date of publication: 2014-04-01
    Journal article

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    A perturb and observe algorithm based on both the power-current characteristic of a photovoltaic (PV) panel and the sliding-mode control of the input inductor current of an associated converter is investigated in a static application. A single ended primary inductance converter (SEPIC) converter charging a battery from a PV generator illustrates the procedure whose effectiveness is proved with experimental results. The reported technique is appropriate for distributed maximum power point tracking of PV systems with output series connected DC-DC switching converters. In these systems, each converter is supplied by an independent PV panel at the input port whereas its output port is connected in series with the output ports of the other converters. The proposed converter interconnection is based on a transformer-less SEPIC because of the capability of this converter to step-up or step-down the input voltage. The resulting system allows maximum power extraction from each PV source even in cases of non-uniform irradiance. © The Institution of Engineering and Technology 2014.

    A perturb and observe algorithm based on both the power-current characteristic of a photovoltaic (PV) panel and the sliding-mode control of the input inductor current of an associated converter is investigated in a static application. A single ended primary inductance converter (SEPIC) converter charging a battery from a PV generator illustrates the procedure whose effectiveness is proved with experimental results. The reported technique is appropriate for distributed maximum power point tracking of PV systems with output series connected DC-DC switching converters. In these systems, each converter is supplied by an independent PV panel at the input port whereas its output port is connected in series with the output ports of the other converters. The proposed converter interconnection is based on a transformer-less SEPIC because of the capability of this converter to step-up or step-down the input voltage. The resulting system allows maximum power extraction from each PV source even in cases of non-uniform irradiance. © The Institution of Engineering and Technology 2014.

  • GUANAY-II:an autonomous underwater vehicle for vertical/horizontal sampling

     Gomariz Castro, Spartacus; Masmitja Rusiñol, Ivan; Gonzalez Agudelo, Julian; Masmitjà, Gerard; Prats, Jordi
    Journal of marine science and technology
    Date of publication: 2014-01-11
    Journal article

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    This paper presents the design and construction of Guanay-II vehicle. It is an autonomous underwater vehicle that navigates over the sea surface and, at certain fixed points, dives vertically to obtain a profile of a water column. It was designed for shallow water, with maximum depth of 30 m. The vehicle uses a cylinder to do the immersions. The cylinder can take in and eject water smoothly, thus it can change the vehicle¿s buoyancy, and avoid creating perturbations in the environment. The designed vehicle has a double-hull structure. The external fiberglass hull, which is not watertight, has been designed in accordance with Myring profiles to provide good hydrodynamic performance. The watertight module located inside the external hull is made of aluminum and contains the immersion actuator, batteries and the electronic system to control the vehicle operations. The control system is divided into several subsystems: navigation, propulsion/immersion, safety, communication and data acquisition. The vehicle is 2300 mm in length by 320 mm in diameter, and weighs 90 kg.

  • Temperature gradient sensor from pulsed power supply duty cycle in ultra-low-power energy harvesting system

     Jove Casulleras, Roger; Ramos Castro, Juan Jose; Corimanya, H; Camps Carmona, Adriano Jose; Alarcon Cot, Eduardo Jose; Amezaga Sarries, Adria; Bou Balust, Elisenda
    Electronics Letters
    Date of publication: 2014-05-22
    Journal article

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    Directly interfacing sensors that link sensors to micro-controllers without a signal conditioning circuit or an analogue-to-digital converter on the one side and energy harvesting systems on the other side are two key enabling technologies to create self-powered autonomous low-cost and low-maintenance sensor networks. In this reported work, both technologies are concurrently combined in such a way that the duty cycle of the pulsed power supply provided by the harvesting system itself yields in turn a temperature gradient sensor functionality. Originally conceived to power a low-power satellite beacon in a CubeSat project, it has found application, among other applications, in automatic air conditioning and heating systems aiming smart buildings.

  • N3Sim: Simulation framework for diffusion-based molecular communication nanonetworks

     Llatser Marti, Ignacio; Demiray, D.; Cabellos Aparicio, Alberto; Atilar, D.; Alarcon Cot, Eduardo Jose
    Simulation modelling practice and theory
    Date of publication: 2014-03-01
    Journal article

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    Diffusion-based molecular communication is a promising bio-inspired paradigm to implement nanonetworks, i.e., the interconnection of nanomachines. The peculiarities of the physical channel in diffusion-based molecular communication require the development of novel models, architectures and protocols for this new scenario, which need to be validated by simulation. N3Sim is a simulation framework for nanonetworks with transmitter, receiver, and harvester nodes using Diffusion-based Molecular Communication (DMC). In DMC, transmitters encode the information by releasing molecules into the medium, thus varying their local concentration. N3Sim models the movement of these molecules according to Brownian dynamics, and it also takes into account their inertia and the interactions among them. Harvesters collect molecules from the environment to reuse them for later transmissions. Receivers decode the information by sensing the particle concentration in their neighborhood. The benefits of N3Sim are multiple: the validation of channel models for DMC and the evaluation of novel modulation schemes are just a few examples. (C) 2013 Elsevier B.V. All rights reserved.

  • Unlocking higher harmonics in atomic force microscopy with gentle interactions

     Santos Hernandez, Sergio; Barcons Xixons, Victor; Font Teixido, Jose; Verdaguer Prats, Albert
    Beilstein Journal of Nanotechnology
    Date of publication: 2014-03-11
    Journal article

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    In dynamic atomic force microscopy, nanoscale properties are encoded in the higher harmonics. Nevertheless, when gentle interactions and minimal invasiveness are required, these harmonics are typically undetectable. Here, we propose to externally drive an arbitrary number of exact higher harmonics above the noise level. In this way, multiple contrast channels that are sensitive to compositional variations are made accessible. Numerical integration of the equation of motion shows that the external introduction of exact harmonic frequencies does not compromise the fundamental frequency. Thermal fluctuations are also considered within the detection bandwidth of interest and discussed in terms of higher-harmonic phase contrast in the presence and absence of an external excitation of higher harmonics. Higher harmonic phase shifts further provide the means to directly decouple the true topography from that induced by compositional heterogeneity.

  • Initial capacitor charging in grid-connected flying capacitor multilevel converters

     Ghias, Amer M.Y.M; Pou Felix, Josep; Agelidis, Vassilios; Ciobotaru, Mihai
    IEEE transactions on power electronics
    Date of publication: 2014-07-01
    Journal article

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    This letter reports a method for the initial charging of capacitors in grid-connected flying capacitor (FC) multilevel converters. A resistor is inserted between each phase of the FC converter and the grid. A voltage balancing algorithm is activated from the beginning of the process and the FC converter generates proper output voltages to achieve balanced charging of both the dc-bus capacitor and the FCs. The proposed initial charging method achieves low voltage and current stress on the power devices and the passive components. The method is simple to implement and can be applied to an FC with any number of levels. Experimental results demonstrate the effectiveness of the proposed method.

    This letter reports a method for the initial charging of capacitors in grid-connected flying capacitor (FC) multilevel converters. A resistor is inserted between each phase of the FC converter and the grid. A voltage balancing algorithm is activated from the beginning of the process and the FC converter generates proper output voltages to achieve balanced charging of both the dc-bus capacitor and the FCs. The proposed initial charging method achieves low voltage and current stress on the power devices and the passive components. The method is simple to implement and can be applied to an FC with any number of levels. Experimental results demonstrate the effectiveness of the proposed method.

  • Global MPPT scheme for photovoltaic string inverters based on restricted voltage window search algorithm

     Boztepe, Mutlu; Guinjoan Gispert, Francisco; Velasco Quesada, Guillermo; Silvestre Berges, Santiago; Chouder, Aissa; Karatepe, Engin
    IEEE transactions on industrial electronics
    Date of publication: 2014-07-01
    Journal article

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    String inverter photovoltaic (PV) systems with bypass diodes require improved global maximum power point tracking (GMPPT) algorithms to effectively reach the absolute maximum power operating point. Several GMPPT algorithms have been proposed to deal with this problem, but most of them require scanning wide voltage ranges of the PV array from nearly zero voltage to open-circuit voltage that increases the scanning time and, in turn, causes energy loss. This paper presents a novel GMPPT method which significantly restricts the voltage window search range and tracks the global power peak rapidly in all shading conditions. Simulation tests and experimental comparisons with another GMPPT algorithm are presented to highlight the features of the presented approach.

    String inverter photovoltaic (PV) systems with bypass diodes require improved global maximum power point tracking (GMPPT) algorithms to effectively reach the absolute maximum power operating point. Several GMPPT algorithms have been proposed to deal with this problem, but most of them require scanning wide voltage ranges of the PV array from nearly zero voltage to open-circuit voltage that increases the scanning time and, in turn, causes energy loss. This paper presents a novel GMPPT method which significantly restricts the voltage window search range and tracks the global power peak rapidly in all shading conditions. Simulation tests and experimental comparisons with another GMPPT algorithm are presented to highlight the features of the presented approach.

  • Voltage-balancing method using phase-shifted PWM for the flying capacitor multilevel converter

     Ghias, Amer M.Y.M; Pou Felix, Josep; Ciobotaru, Mihai; Agelidis, Vassilios
    IEEE transactions on power electronics
    Date of publication: 2014-09
    Journal article

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    Multilevel flying capacitor (FC) converters provide natural capacitor voltage balance under phase-shifted pulse width modulation (PS-PWM). However, natural balancing may not be robust enough to maintain the voltages at the reference values, especially under certain transient conditions. Furthermore, natural balancing dynamics depend on the load and it may be very slow in some practical applications. Therefore, a more robust balancing mechanism of maintaining the FC voltages at the desired values is required. This paper proposes a new closed-loop voltage-balancing method for the multilevel FC converters using PS-PWM. The proposed method balances the voltages of the FCs by modifying the duty cycle of each switch of the FC converter using a proportional controller. The crossed effect between FC currents and duty cycles is considered and is used for optimal FC voltage balancing. Simulation and experimental results verify that the proposed voltage-balancing method is very robust to different operating conditions, such as load transients, linear/nonlinear and unbalanced loads

    Multilevel flying capacitor (FC) converters provide natural capacitor voltage balance under phase-shifted pulse width modulation (PS-PWM). However, natural balancing may not be robust enough to maintain the voltages at the reference values, especially under certain transient conditions. Furthermore, natural balancing dynamics depend on the load and it may be very slow in some practical applications. Therefore, a more robust balancing mechanism of maintaining the FC voltages at the desired values is required. This paper proposes a new closed-loop voltage-balancing method for the multilevel FC converters using PS-PWM. The proposed method balances the voltages of the FCs by modifying the duty cycle of each switch of the FC converter using a proportional controller. The crossed effect between FC currents and duty cycles is considered and is used for optimal FC voltage balancing. Simulation and experimental results verify that the proposed voltage-balancing method is very robust to different operating conditions, such as load transients, linear/nonlinear and unbalanced loads

  • Some limits in peer assessment

     Domingo Peña, Joan; Martínez García, Herminio; Gomariz Castro, Spartacus; Gamiz Caro, Juan
    Journal of technology and science education
    Date of publication: 2014-03-25
    Journal article

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    Nowadays, the educational methodology known as `peer assessment¿ constitutes one of the pillars of formative assessment at the different levels of the educational system, particularly at the University level. In fact, in recent years, it has been increasingly used to enhance students' meaningful learning, as it is considered to be an element of social learning, in which students benefit from the lessons learned by other classmates, and draw upon the ability to assess the quality of the learning, contrasting it with the level of knowledge that each has about the subject/course being evaluated, and using common evaluation criteria. In this regard, this paper represents the experience of two groups of students. It allows us to determine how many peer assessments should be required of students in a particular course in order to constitute a serious, reliable activity. On the other hand, from the point of view of the student, the assessments are evaluated to the extent that they are seen as a required and mandatory exercise that must be carried out by students simply to pass the course. In the latter case, the activity can become extremely trivial and banal. Statistical analysis of the results indicates that three peer assessments per student appraised represents an adequate number. On the other hand, more than thirty peer assessments fail to contribute to learning, nor do they represent serious activities.

  • FPGA implementation of a PWM for a three-phase DC-AC multilevel active-clamped converter

     Lupon Roses, Emilio Jose; Busquets Monge, Sergio; Nicolás Apruzzese, Joan
    IEEE transactions on industrial informatics
    Date of publication: 2014-05
    Journal article

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    With the aim to implement a suitable controller for a three-phase dc-ac multilevel active-clamped converter to enable its use in practice, and as a first step toward a full closed-loop converter control implementation into a single field-programmable gate array (FPGA) device, this paper presents the structure and features of an FPGA implementation of an appropriate pulsewidth modulation (PWM) strategy. The selected PWM strategy guarantees dc-link capacitor voltage balance in every switching cycle, and covers both the undermodulation and overmodulation regions. A flexible implementation is conceived, allowing the variation of important operating parameters, such as the modulation index and switching frequency, through a simple user interface. The key aspects to achieve an efficient and robust FPGA implementation are discussed. Experimental results in a four-level converter prototype controlled with an Altera Cyclone III device under different operating conditions match fairly well with the expected results obtained through simulation, thus verifying the accurate performance of the FPGA-based modulator

    With the aim to implement a suitable controller for a three-phase dc-ac multilevel active-clamped converter to enable its use in practice, and as a first step toward a full closed-loop converter control implementation into a single field-programmable gate array (FPGA) device, this paper presents the structure and features of an FPGA implementation of an appropriate pulsewidth modulation (PWM) strategy. The selected PWM strategy guarantees dc-link capacitor voltage balance in every switching cycle, and covers both the undermodulation and overmodulation regions. A flexible implementation is conceived, allowing the variation of important operating parameters, such as the modulation index and switching frequency, through a simple user interface. The key aspects to achieve an efficient and robust FPGA implementation are discussed. Experimental results in a four-level converter prototype controlled with an Altera Cyclone III device under different operating conditions match fairly well with the expected results obtained through simulation, thus verifying the accurate performance of the FPGA-based modulator

  • Contributions on corona onset voltage calculation for EHV and UHV substation connectors

     Hernandez Guiteras, Joan
    Defense's date: 2014-03-28
    Universitat Politècnica de Catalunya
    Theses

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    Les investigacions realitzades en aquesta tesi es va realitzar en el marc d'un acord empresa - universitat . L'objectiu d'aquesta investigació és determinar la tensió d'inici de l'efecte corona en geometries no uniformes per evitar la seva aparició, i així poder incidir en la fase de disseny del connectors de subestació de EHV i UHV i equipmanet auxiliar de línia instal·lats en condicions de funcionament, d'acord amb les normes internacionals . Per tant , s'ha prestat una consideració especial a l'estudi i el modelatge de l'efecte corona per assegurar que els connectors dissenyats es trobin gairebé lliures d'aquest efecte indesitjable . Degut a de la natura d'aquest acord marc, la investigació científica s'ha vist delimitada a l'aplicabilitat en un entorn industrial a fi d'obtenir la accreditació, segons les normatives internacionals, dels productes analitzats.Per tant , els temes tractats en aquesta investigació inclouen l'anàlisi de camps electromagnètics i els càlculs de l'efecte corona , sent aquest últim de gran importància en el disseny dels connectors de subestació per EHV i UHV . És objectiu d'aquesta tesi proporcionar augmentar el coneixement i aportar mètodes matemàtics apropiats per avaluar el comportament dielèctric de connectors de subestació per a sistemes de transmissió de EHV i UHV . En concret , s'ha destinat un capítol a la introducció a l'estat de la tècnica en connectors de la subestació i l'efecte corona, seguit d'un capítol adreçat a l'estudi dels camps elèctrics i magnètics creats pels connectors de la subestació i les equacions empíriques per al càlcul de l'effecte corona. A continuació, s'introdueix una descripció macroscòpica del corona a través de la descripció matemàtica del procés de ionització, tant des del cas estacionari com el transitori. Seguit de la descripció microscòpica a través de funcions de distribució estadístiques utilitzdes per descriure i calcular els paràmetres d'ionització del corona en l'aire . Finalment, es troba el capítol de tancament amb les principals aportacions de la investigació realitzada.

  • On the Scalability Limits of Communication Networks to the Nanoscale  Open access

     Llatser Marti, Ignacio
    Defense's date: 2014-01-17
    Universitat Politècnica de Catalunya
    Theses

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    Los nanosistemas, sistemas integrados con un tamaño total de unos pocos micrómetros, son capaces de interactuar en la nanoescala, pero su corto radio de acción limita su utilidad en escenarios prácticos. Las nanoredes, que surgen de la interconexión de nanosistemas, amplían su ámbito de operación permitiendo la comunicación entre nanosistemas, aumentando de esta forma sus aplicaciones potenciales. Con el fin de dotar de capacidades de comunicación a los nanosistemas, su subsistema de comunicación debe reducirse a unos pocos micrómetros. Existen dudas sobre la viabilidad de miniaturizar las antenas metálicas actuales a un tamaño tan pequeño, especialmente porque su frecuencia de resonancia sería extremadamente alta (en el espectro óptico), lo que causaría a una gran atenuación de las ondas radiadas. Como alternativa, se han propuesto dos nuevos paradigmas para implementar comunicaciones inalámbricas entre nanosistemas: las comunicaciones moleculares y las comunicaciones inalámbricas basadas en grafeno. Por un lado, las comunicaciones moleculares consisten en el intercambio de moléculas entre nanosistemas, inspirado en la comunicación entre células vivas. En las comunicaciones moleculares basadas en difusión (DMC), las moléculas emitidas se propagan por el medio mediante un proceso de difusión hasta que alcanzan el receptor. Por otro lado, el grafeno (una lámina de átomos de carbono de un átomo de espesor) permite implementar antenas de grafeno plasmónicas, o grafenas. Debido a efectos plasmónicos, grafenas con un tamaño de unos pocos micrómetros radian ondas en la banda de terahercios, dando lugar al paradigma de las comunicaciones inalámbricas basadas en grafeno (GWC). Para averiguar cómo escalan las redes de comunicación a medida que se reducen sus dimensiones, esta tesis se presenta un análisis de la escalabilidad de las redes de comunicaciones hacia la nanoescala, siguiendo un modelo general con la menor cantidad posible de hipótesis. Hemos propuesto dos esquemas de detección en DMC: detección de amplitud y detección de energía. Hemos identificado importantes métricas de rendimiento y calculado su escalabilidad con respecto a la distancia de transmisión, que difiere significativamente respecto a las comunicaciones inalámbricas tradicionales. Estas nuevas tendencias de escala requieren el diseño de nuevos protocolos de red especialmente adaptados a las redes de DMC. El análisis de la propagación de ondas plasmónicas en grafenas permite determinar sus propiedades de radiación. En particular, la frecuencia de resonancia de las grafenas no sólo es más baja que en antenas metálicas, sino que también aumenta más lentamente a medida que reducimos su longitud. Por otra parte, la frecuencia de resonancia de las grafenas puede ser ampliamente controlada en función de parámetros como las dimensiones de la grafena, el tiempo de relajación del grafeno y el potencial químico. Además, proponemos un montaje experimental que permite la medición de grafenas alimentadas con una fuente fotoconductora. También hemos analizado los efectos de la absorción molecular en el canal de terahercios a corto alcance, el escenario de operación de las grafenas. La absorción molecular es un proceso por el cual moléculas presentes en la atmósfera absorben parte de la energía de las ondas radiadas por las grafenas, degradando su rendimiento. Hemos cuantificado esta degradación derivando parámetros de rendimiento en este escenario, que muestran novedosas tendencias de escalabilidad en función de la distancia de transmisión. Por último, hemos encontrado que la capacidad de canal de GWC escala mejor a medida que el tamaño de la antena se reduce con respecto a las comunicaciones inalámbricas tradicionales. En consecuencia, las GWC requerirán una potencia de transmisión más baja para lograr un cierto rendimiento. Estos resultados establecen un marco general que puede servir de guía para diseñar las futuras redes de comunicaciones inalámbricas entre nanosistemas.

    Nanosystems, integrated systems with a total size of a few micrometers, are capable of interacting at the nanoscale, but their short operating range limits their usefulness in practical macro-scale scenarios. Nanonetworks, the interconnection of nanosystems, will extend their range of operation by allowing communication among nanosystems, thereby greatly enhancing their potential applications. In order to integrate communication capabilities into nanosystems, their communication subsystem needs to shrink to a size of a few micrometers. There are doubts about the feasibility of scaling down current metallic antennas to such a small size, mainly because their resonant frequency would be extremely high (in the optical domain) leading to a large free-space attenuation of the radiated EM waves. In consequence, as an alternative to implement wireless communications among nanosystems, two novel paradigms have emerged: molecular communication and graphene-enabled wireless communications. On the one hand, molecular communication is based on the exchange of molecules among nanosystems, inspired by communication among living cells. In Diffusion-based Molecular Communication (DMC), the emitted molecules propagate throughout the environment following a diffusion process until they reach the receiver. On the other hand, graphene, a one-atom-thick sheet of carbon atoms, has been proposed to implement graphene plasmonic RF antennas, or graphennas. Graphennas with a size in the order of a few micrometers show plasmonic effects which allow them to radiate EM waves in the terahertz band. Graphennas are the enabling technology of Graphene-enabled Wireless Communications (GWC). In order to answer the question of how communication networks will scale when their size shrinks, this thesis presents a scalability analysis of the performance metrics of communication networks to the nanoscale, following a general model with as few assumptions as possible. In the case of DMC, two detection schemes are proposed: amplitude detection and energy detection. Key performance metrics are identified and their scalability with respect to the transmission distance is found to differ significantly from the case of traditional wireless communications. These unique scaling trends present novel challenges which require the design of novel networking protocols specially adapted to DMC networks. The analysis of the propagation of plasmonic waves in graphennas allows determining their radiation performance. In particular, the resonant frequency of graphennas is not only lower than in metallic antennas, but it also increases more slowly as their length is reduced to the nanoscale. Moreover, the study of parameters such as the graphenna dimensions, the relaxation time of graphene and the applied chemical potential shows the tunability of graphennas in a wide frequency range. Furthermore, an experimental setup to measure graphennas based on feeding them by means of a photoconductive source is described. The effects of molecular absorption in the short-range terahertz channel, which corresponds to the expected operating scenario of graphennas, are analyzed. Molecular absorption is a process in which molecules present in the atmosphere absorb part of the energy of the terahertz EM waves radiated by graphennas, causing impairments in the performance of GWC. The study of molecular absorption allows quantifying this loss by deriving relevant performance metrics in this scenario, which show novel scalability trends as a function of the transmission distance with respect to the case of free-space propagation. Finally, the channel capacity of GWC is found to scale better as the antenna size is reduced than in traditional wireless communications. In consequence, GWC will require lower transmission power to achieve a given performance target. These results establish a general framework which may serve designers as a guide to implement wireless communication networks among nanosystems.

  • 17è Premi a la Qualitat en la Docència Universitària del Consell Social de la UPC al `Grau en Enginyeria de Sistemes TIC¿

     Palà Schönwälder, Pere; Argelaguet Isanta, Maria Rosa; Barcons Xixons, Victor; Bonet Dalmau, Jordi; del Águila López, Francisco; Escobet Canal, Teresa; Escobet Canal, Antoni; Font Teixido, Jose; Giralt Mas, M. Rosa; Lopez Riera, Alexis; Llusà Serra, Aleix; Martinez Teixidor, Inmaculada; Tarres Puertas, Marta Isabel; Vicente Rodrigo, Jesús; Vila Marta, Sebastian
    Award or recognition

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  • IPT-2011-1543-920000-Anualitat 2014

     Romeral Martinez, Jose Luis
    Participation in a competitive project

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  • Non-linear Control Algorithms for Enhanced Stability in Inverter-Based Microgrid

     Romeral Martinez, Jose Luis
    Participation in a competitive project

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  • Fault Diagnosis and Fault Tolerant Control of Multiphase Voltage Source Converters For Application in Traction Drives

     Salehifar, Mehdi
    Defense's date: 2014-07-15
    Department of Electronic Engineering, Universitat Politècnica de Catalunya
    Theses

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    Hay una creciente demanda de vehículos con menor impacto ambiental y una mayoreficiencia de combustible. Para cumplir estos requisitos, la electrificación del transporte se ha introducido en la academia y la industria en los últimos años. Vehículos eléctricos y vehículos eléctricos híbridos son dos ejemplos prácticos en los sistemas de transporte.El tren de potencia típico en los vehículos eléctricos se compone de tres partes principales, incluyendo la fuente de energía, la electrónica de potencia y un motor eléctrico. En cuanto a la máquina, de imán permanente motores son la opción dominante para vehículos híbridos ligeros en la industria debido a su mayor eficiencia y densidad de potencia. Con el fin de operar el tren de potencia, la máquina eléctrica se puede suministrar y controlado por un inversor de fuente de tensión. El convertidor se somete a diversos tipos de fallos. Según las estadísticas, 38 % de las fallas en un motor se deben al convertidor de potencia.Por otro lado, el tren de potencia eléctrica debe cumplir con un alto nivel de fiabilidad.Máquinas multifase PM pueden cumplir con los requisitos de fiabilidad debido a suscaracterísticas de tolerancia a fallos. La máquina puede seguir siendo operativo con fallas en múltiples fases. En consecuencia, para realizar una unidad de motor de alta disponibilidad de múltiples fases, tres conceptos principales deben desarrollarse incluyendo la detección de fallos, el aislamiento de fallas y control tolerante a fallos. Por tanto, esta tesis doctoral se centra en la FD y control tolerante a fallos de un VSI multifase.Para lograr este objetivo la investigación, los productos alimenticios y bebidas y métodos de control que se presentan del convertidor de potencia se investigan a fondo a través de revisión de la literatura. Después de eso, se estudió la condición operativa del convertidor de múltiples el suministro de la máquina eléctrica.En cuanto a los métodos de FD en múltiples fases, tres nuevos algoritmos se presentan en esta tesis. Estos métodos FD propuestas también están integrados en los nuevos algoritmos de control con tolerancia a fallos. En el primer paso, se propone un método FD modelo novela basada detectar fallas múltiples del interruptor abierto. Este método FD está incluido en el algoritmo de control adaptativo desarrollado proporcional resonante del convertidor de potencia.En el segundo paso, se proponen dos métodos FD señal basada. Se discute el control tolerante a fallos del convertidor de potencia con el controlador PI convencional. Además, la teoría de la SMC se desarrolla. En el último paso, el control conjunto finito modelo de control predictivo del motor de cinco fases sin escobillas de corriente continua se discutió por primera vez en estatesis. Un método FD sencilla se deriva de las señales de control. Las entradas a todos los métodos desarrollados son las corrientes de cinco de fase del motor.La teoría de cada método se explica y se compara con los métodos disponibles. Paravalidar la teoría desarrollada en cada parte, FD algoritmo está incorporado en el algoritmo de control tolerante a fallos. Los resultados experimentales se llevan a cabo en una unidad de motor BLDC de cinco fases. El motor eléctrico usado en los resultados experimentales tiene una estructura de rotor exterior en las cuatro ruedas. Este motor es adecuado para los vehículos eléctricos. Al final de cada parte, se presentan los puntos notables y conclusiones.

  • Integració de la competència de la tercera llengua en els estudis de grau

     Alsina Aubach, Montserrat; Argelaguet Isanta, Maria Rosa; Bonet Dalmau, Jordi; de las Heras Cisa, F. Xavier; del Águila López, Francisco; Fortuny Santos, Jordi; Franch Parella, Jorge; Gamisans Noguera, Javier; Giralt Mas, M. Rosa; Lao Luque, Concepcion; Martinez Teixidor, Inmaculada; Palà Schönwälder, Pere; Parcerisa Duocastella, David; Vicente Rodrigo, Jesús; Lopez Martinez, Joan Antoni; Soler Lorente, Monica; Vila Marta, Sebastian
    Higher Education Perspectives on CLIL
    Presentation's date: 2014-03-28
    Presentation of work at congresses

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  • A rolling horizon rescheduling strategy for flexible energy in a microgrid

     Marietta, Martín Pablo; Graells Sobre, Moises; Guerrero Zapata, Josep Maria
    IEEE International Energy Conference and Exhibition
    Presentation's date: 2014-05-16
    Presentation of work at congresses

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    In this work an Energy Management System (EMS) prototype for an isolated renewable-based microgrid is presented. The proposed management model not only considers the management of energy sources (generation) but also includes the possibility of flexible timing of energy consumptions (demand management) by modelling controllable and uncontrollable loads. The EMS consists of two stages: first a deterministic management model is formulated and subsequently is integrated into a rolling horizon control strategy, in which the actions on microgrid devices respond to an optimization criterion related to the estimation of the future system behaviour that is continually predicted by updatable forecasts in order to reduce uncertainty in both, production capacity and energy demand. Finally, this contribution presents and discusses a case study where the results of the operation with and without optimal demand management for the same group of loads are evaluated.

  • Planificació de la impartició d'assignatures en anglès a l'EPSEM

     Alsina Aubach, Montserrat; Argelaguet Isanta, Maria Rosa; Martinez Teixidor, Inmaculada; Vicente Rodrigo, Jesús
    Higher Education Perspectives on CLIL
    Presentation's date: 2014-03-27
    Presentation of work at congresses

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  • Class E2 resonant non-radiative wireless power transfer link: a design-oriented joint circuit-system co-characterization approach

     Bou Balust, Elisenda; Nagashima, Tomoharu; Sekiya, Hiroo; Alarcon Cot, Eduardo Jose
    International Multi-Conference on Systems, Signals and Devices
    Presentation's date: 2014-02-11
    Presentation of work at congresses

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    Resonant Inductive CouplingWireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. Many applications have been proposed for this technology, but the interplay between the Resonant Inductive Coupling magnetic link and the power electronics front-end is still unclear. In this paper, we propose a design-oriented joint circuit-system approach to design a high-efficiency resonant inductive coupling wireless power transfer link embedded in a class E2 DC-DC converter. © 2014 IEEE.

    Resonant Inductive CouplingWireless Power Transfer is a key technology to provide an efficient and harmless wireless energy channel to consumer electronics, biomedical implants and wireless sensor networks. Many applications have been proposed for this technology, but the interplay between the Resonant Inductive Coupling magnetic link and the power electronics front-end is still unclear. In this paper, we propose a design-oriented joint circuit-system approach to design a high-efficiency resonant inductive coupling wireless power transfer link embedded in a class E2 DC-DC converter. © 2014 IEEE.

  • Performance analysis of dual-frequency buck converter for integrated power management

     Shirmohammadli, V.; Saberkari, Alireza; Alarcon Cot, Eduardo Jose
    Power Electronics, Drive Systems and Technologies Conference
    Presentation's date: 2014-02
    Presentation of work at congresses

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    The use of dual-frequency (DF) buck converter architecture consisting of a merged structure of high and low frequency buck cells is presented as a candidate topology for integrated power management to obtain favorable tradeoffs in terms of efficiency, switching ripple, and bandwidth. It is shown that having two degrees of freedom in designing the DF buck helps to achieve high efficiency and low output ripples, simultaneously. A comparison analysis is done with regards to the aforementioned performance indexes with the standard and three-level buck converters and the results are validated in HSPICE in a 0.35 µm CMOS process.

    The use of dual-frequency (DF) buck converter architecture consisting of a merged structure of high and low frequency buck cells is presented as a candidate topology for integrated power management to obtain favorable tradeoffs in terms of efficiency, switching ripple, and bandwidth. It is shown that having two degrees of freedom in designing the DF buck helps to achieve high efficiency and low output ripples, simultaneously. A comparison analysis is done with regards to the aforementioned performance indexes with the standard and three-level buck converters and the results are validated in HSPICE in a 0.35 µm CMOS process.

  • A modified voltage balancing sorting algorithm for the modular multilevel converter: Evaluation for staircase and phase-disposition PWM

     Darus, Rosheila; Pou Felix, Josep; Konstantinou, Georgios; Ceballos Recio, Salvador; Agelidis, Vassilios
    IEEE Applied Power Electronics Conference and Exposition
    Presentation's date: 2014-03
    Presentation of work at congresses

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    This paper introduces a low complexity implementation of the voltage balancing sorting algorithm to reduce the switching frequency of the power devices in modular multilevel converters (MMCs). Two modulation techniques are evaluated; staircase modulation and phase-disposition pulse-width modulation (PD-PWM) under the conventional and the proposed algorithm. Using a circulating current controller in an MMC with 12 sub-modules per arm, PD-PWM yields better results compared to the staircase modulation technique. The test condition for this comparison is such that the power devices operate at a similar switching frequency and produce similar amplitudes to the capacitor voltage ripples in both modulation techniques. The results are verified through extensive simulations and experimentally using a phase-leg MMC laboratory prototype.

    This paper introduces a low complexity implementation of the voltage balancing sorting algorithm to reduce the switching frequency of the power devices in modular multilevel converters (MMCs). Two modulation techniques are evaluated; staircase modulation and phase-disposition pulse-width modulation (PD-PWM) under the conventional and the proposed algorithm. Using a circulating current controller in an MMC with 12 sub-modules per arm, PD-PWM yields better results compared to the staircase modulation technique. The test condition for this comparison is such that the power devices operate at a similar switching frequency and produce similar amplitudes to the capacitor voltage ripples in both modulation techniques. The results are verified through extensive simulations and experimentally using a phase-leg MMC laboratory prototype.

  • Observation of chaotic behavior in automatic tuning loops for continuous-time filters

     Martínez García, Herminio; Cosp Vilella, Jordi; Manzanares Brotons, Manuel
    IEEE International Midwest Symposium on Circuits and Systems
    Presentation's date: 2014-08
    Presentation of work at congresses

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    he appropriate linear dynamic modeling of continuous-time filters (CTFs) with automatic tuning loops should be obtained to assure stability in case an improved design of the loop controllers is to be carried out. With this aim, starting from a general and systematic analysis in order to obtain an equivalent small-signal linearized incremental model, from which transfer functions between output variables and control voltages are derived, the subsequent design of compensated loops with enhanced stability and dynamic performance is required. This systematic procedure allows obtaining improved controllers for the two involved control loops. However, CTFs with automatic tuning loops are nonlinear feedback systems with potential instability. What is more, nonlinear phenomena, which cannot be predicted by a design-oriented small signal modeling approach, are observed in this kind of tuning systems. The purpose of this work is to highlight that when control parameters are varied, the system could present different kinds of dynamical nonlinear phenomena such as bifurcations and chaotic behavior, which cannot be predicted by the small signal design-oriented model.

    he appropriate linear dynamic modeling of continuous-time filters (CTFs) with automatic tuning loops should be obtained to assure stability in case an improved design of the loop controllers is to be carried out. With this aim, starting from a general and systematic analysis in order to obtain an equivalent small-signal linearized incremental model, from which transfer functions between output variables and control voltages are derived, the subsequent design of compensated loops with enhanced stability and dynamic performance is required. This systematic procedure allows obtaining improved controllers for the two involved control loops. However, CTFs with automatic tuning loops are nonlinear feedback systems with potential instability. What is more, nonlinear phenomena, which cannot be predicted by a design-oriented small signal modeling approach, are observed in this kind of tuning systems. The purpose of this work is to highlight that when control parameters are varied, the system could present different kinds of dynamical nonlinear phenomena such as bifurcations and chaotic behavior, which cannot be predicted by the small signal design-oriented model.

  • High slew rate current mode transconductance error amplifier for low quiescent current output-capacitorless CMOS LDO regulator

     Fathipour, Rasoul; Saberkari, Alireza; Martínez García, Herminio; Alarcon Cot, Eduardo Jose
    Integration. The VLSI journal
    Date of publication: 2013-11-08
    Journal article

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    This paper presents a CMOS low quiescent current output-capacitorless low-dropout regulator (LDO) based on a high slew rate current mode transconductance amplifier (CTA) as error amplifier. Using local common-mode feedback (LCMFB) in the proposed CTA, the order of transfer characteristic of the circuit is increased. Therefore, the slew rate at the gate of pass transistor is enhanced. This improves the LDO load transient characteristic even at low quiescent current. The proposed LDO topology has been designed and post simulated in HSPICE in a 0.18 µm CMOS process to supply the load current between 0-100 mA. The dropout voltage of the LDO is set to 200 mV for 1.2-2 V input voltage. Post-layout simulation results reveal that the proposed LDO is stable without any internal compensation strategy and with on-chip output capacitor or lumped parasitic capacitances at the output node between 10-100 pF. The total quiescent current of the LDO including the current consumed by the reference buffer circuit is only 3.7 µA. A final benchmark comparison considering all relevant performance metrics is presented.

  • Active redundant submodule configuration in modular multilevel converters

     Konstantinou, Georgios; Pou Felix, Josep; Ceballos Recio, Salvador; Agelidis, Vassilios
    IEEE transactions on power delivery
    Date of publication: 2013-09
    Journal article

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    The modular multilevel converter (MMC) is based on the cascaded connection of identical submodules (SMs) enabling additional redundancies. This paper proposes the configuration of the MMC topology with redundant SMs and demonstrates the effects of active redundancies. The proposed configuration decreases the switching frequency per SM while reducing the SM capacitor voltage ripples. An analytical model for determining the SM capacitor voltage ripple and voltage dynamics is derived. The results from the analytical model are compared with the switching model for a 21-level MMC with five redundant (25 in total) SMs per arm. Experimental results based on a single-phase laboratory prototype with five SMs per arm and a single redundant cell further illustrate the operation and verify the derived mathematical model and simulation results.

    The modular multilevel converter (MMC) is based on the cascaded connection of identical submodules (SMs) enabling additional redundancies. This paper proposes the configuration of the MMC topology with redundant SMs and demonstrates the effects of active redundancies. The proposed configuration decreases the switching frequency per SM while reducing the SM capacitor voltage ripples. An analytical model for determining the SM capacitor voltage ripple and voltage dynamics is derived. The results from the analytical model are compared with the switching model for a 21-level MMC with five redundant (25 in total) SMs per arm. Experimental results based on a single-phase laboratory prototype with five SMs per arm and a single redundant cell further illustrate the operation and verify the derived mathematical model and simulation results.

  • Fault detection and fault tolerant operation of a five phase PM motor drive using adaptive model identification approach

     Salehifar, Mehdi; Salehi Arashloo Arashloo, Ramin; Moreno Eguilaz, Juan Manuel; Sala Caselles, Vicente Miguel; Romeral Martinez, Jose Luis
    IEEE Journal of emerging and selected topics in power electronics
    Date of publication: 2013-12-03
    Journal article

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  • Energy-balance control of PV cascaded multilevel grid-connected inverters for phase-shifted and level-shifted pulse-width modulations

     Chavarria Roe, Javier; Biel Sole, Domingo; Guinjoan Gispert, Francisco; Meza Benavides, Carlos; Negroni Vera, Juan José
    IEEE transactions on industrial electronics
    Date of publication: 2013-01
    Journal article

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    This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent photovoltaic (PV) arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array, ensuring the stability of the system for the whole range of PV array operating conditions. The control design is adapted to phase-shifted and level-shifted carrier pulsewidth modulations to share the control action among the cascade-connected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a seven-level inverter are included to validate the proposed approach.

    This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent PV arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array ensuring the stability of the system for the whole range of PV arrays operating conditions. The control design is adapted to Phase-Shifted and Level-Shifted Carrier PWM to share the control action among the cascadeconnected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a 7-level inverter are included to validate the proposed approach.

  • Efficiency optimization in low inertia wells turbine-oscillating water column devices

     Ceballos Recio, Salvador; Rea, Judy; López, Iraide; Pou Felix, Josep; Robles Sestafe, Eider; Osullivan, Dara
    IEEE transactions on energy conversion
    Date of publication: 2013-09
    Journal article

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    The Wells turbine is a bidirectional air turbine which operates efficiently over a restricted range of air flow. The optimization of its efficiency requires control of rotational velocity in order to maintain the ratio between airflow and tip speed within the high efficiency range. This paper introduces two generator control strategies that optimize the power take-off efficiency for low inertia turbine systems in which instantaneous control of the turbine air flow to tip speed ratio is a realistic goal. The first control strategy requires measurement of turbine rotational speed and air chamber pressure, and the second strategy removes the requirement for air pressure measurement. The implementation issues associated with this level of control are examined and the simulation results are validated in an experimental test rig.

    The Wells turbine is a bidirectional air turbine which operates efficiently over a restricted range of air flow. The optimization of its efficiency requires control of rotational velocity in order to maintain the ratio between airflow and tip speed within the high efficiency range. This paper introduces two generator control strategies that optimize the power take-off efficiency for low inertia turbine systems in which instantaneous control of the turbine air flow to tip speed ratio is a realistic goal. The first control strategy requires measurement of turbine rotational speed and air chamber pressure, and the second strategy removes the requirement for air pressure measurement. The implementation issues associated with this level of control are examined and the simulation results are validated in an experimental test rig.

  • Hybrid sensorless permanent magnet synchronous machine four quadrant drive based on direct matrix converter

     Arias Pujol, Antoni; Ortega, Carlos; Zaragoza Bertomeu, Jordi; Espina, Jordi; Pou Felix, Josep
    International journal of electrical power and energy systems
    Date of publication: 2013-02
    Journal article

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    Permanent Magnet Synchronous Machines (PMSMs) have several advantages, such as high ef¿ciency and low volume and weight, which make them attractive for aerospace applications and high performance servo drives. Matrix Converters (MCs) are an all-silicon alternative, with no bulky reactive elements, to the standard voltage source inverter. The most common control technique for such PMSM MC-fed drives is the so-called Field-Oriented Control (FOC), which requires the permanent magnet ¿ux position to achieve high dynamic performance. Encoders or resolvers are the most common sensing devices used for such a purpose, which not only increases the total cost of the PMSM drive but also adds extra electronics and cabling that may cause failures. This paper investigates and proposes an all range (from zero to full) speed hybrid sensorless FOC. The novelty of this paper relies on the use of a hybrid sensorless four quadrant FOC that averages the needed angle estimation from a model based angle estimator and a voltage pulse test injection angle estimator when feeding the PMSM with an MC instead of a standard voltage source inverter. Speed reversal and load impact simulation results are included, fully supporting the claims made in this paper

  • Sliding mode controlled multiphase buck converter with interleaving and current equalization

     Ramos Lara, Rafael Ramon; Biel Sole, Domingo; Fossas Colet, Enric; Griño Cubero, Roberto
    Control engineering practice
    Date of publication: 2013-05
    Journal article

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    This paper presents a sliding mode control design of a multiphase power converter. The use of multiphase converters and an appropriate phase shift result in chattering reduction to the desired level at a given switching frequency in the so called ¿ripple cancellation¿ or ¿harmonic cancellation¿. Additionally, this strategy considers sliding mode as a suitable substitute for Pulse Width Modulation because of the benefits in sliding mode control, i.e. the possibility of achieving desired system responses regardless of parameter changes. A 4-phase buck converter prototype was built and the controller was programmed in an FPGA. Experimental results show that chattering reduction, robust output regulation and phase current equalization are achieved, thus validating the proposed approach.

  • Access to the full text
    Single-cycle atomic force microscope force reconstruction: Resolving time-dependent interactions  Open access

     Santos, Sergio M.; Gadelrab, Karim Raafat; Font Mateu, Josep; Chiesa, Matteo
    New journal of physics
    Date of publication: 2013-08
    Journal article

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    Here, we enhance the capabilities of the atomic force microscope (AFM) to show that force profiles can be reconstructed without restriction by monitoring the wave profile of the cantilever during a single oscillation cycle. Two approaches are provided to reconstruct the force profile in both the steady and transient states in what we call single-cycle measurements. The robustness of the formalism is tested numerically to recover complex but relevant interactions. With single-cycle measurements, we add high temporal resolution (possibly microsecond range) to the spatial resolution of AFM. The access to simultaneous high throughput and high sensitivity further opens the door to a variety of feedback options for imaging.

    Here, we enhance the capabilities of the atomic force microscope (AFM) to show that force profiles can be reconstructed without restriction by monitoring the wave profile of the cantilever during a single oscillation cycle. Two approaches are provided to reconstruct the force profile in both the steady and transient states in what we call single-cycle measurements. The robustness of the formalism is tested numerically to recover complex but relevant interactions. With single-cycle measurements, we add high temporal resolution (possibly microsecond range) to the spatial resolution of AFM. The access to simultaneous high throughput and high sensitivity further opens the door to a variety of feedback options for imaging

  • Improved switching strategy for selective harmonic elimination in DC-AC signal generation via pulse-width modulation

     Palacios Quiñonero, Francisco; Vicente Rodrigo, Jesús; Molina Hernandez, M. Antonia; Karimi, Hamid Reza
    Abstract and applied analysis
    Date of publication: 2013
    Journal article

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    We present an advanced designmethodology for pulse-width-modulated (PWM) DC-AC signal generation. Using designmethods based on theWalsh transform, AC sinusoidal signals can be approximated by suitable PWMsignals. For different AC amplitudes, the switching instants of the PWM signals can be efficiently computed by using appropriate systems of explicit linear equations. However, the equation systems provided by conventional implementations of this approach are typically only valid for a restricted interval of AC amplitudes and, in general, a supervised implementation of several equation systems is necessary to cover the full AC amplitude range. Additionally, obtaining suitable equation systems for designs with a large number of switching instants requires solving a complex optimization problem. In defining the constitutive pulses of a PWMsignal, a suitable partition of the time interval is used as a reference system. In the new methodology, pulses are chosen to be symmetric with respect to the partition points, and the switching times are specified by means of switching ratios with respect to the endpoint subintervals. This approach leads to particularly simple Walsh series representations, introduces a remarkable computational simplification, and achieves excellent results in reducing the harmonic distortion.